Re: [2/3] mm: fix up some user-visible effects of the stack guard page

On Fri, 2010-08-20 at 17:32 +0100, Ian Campbell wrote:

> On Fri, 2010-08-20 at 09:07 -0700, Linus Torvalds wrote:> > > Actually, thinking some more about it, that may not be a good idea.> > Why? Simply because we may want to merge the vma's back together if> > you do munlock. And it won't (and mustn't) merge if the vm_flags> > differ in VM_GROWSDOWN.> > > > So I do think we want to keep VM_GROWSDOWN (and VM_GROWSUP on> PA-RISC)> > even across a vma split.> > I naively hacked something together and it did seem to work, but I> shared your worries about merging.> > > Of course, we could set a flag whether the vma really does have a> > guard page or not.> > Bits in vma->vm_flags seems to be in rather short supply :-(

On the other hand the VMA merging is just an optimisation, isn't it?

-- Ian Campbell

Many people are desperately looking for some wise advice which willrecommend that they do what they want to do.